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a large change in momentum over a short period of time
a running dog
Conservation of Linear Momentum (CM)
CM → m₁u₁+m₂u₂ = m₁v₁+m₂v₂
NEL → − e = (New Velocity) ÷ (Old Velocity)
Newtons Experimental Law for impacts (NEL) (a ball hits the ground)
e = 1
Coefficient of Restitution, e for an perfectly elastic collision:
e = 0
Coefficient of Restitution, e for an perfectly inelastic collision:
0 ≤ e ≤ 1
Range of value that "e" can have:
Newtons Experimental Law (NEL):
NEL → − e = (v₁ − v₂) ÷ (u₁ − u₂)
Solve: Direct Collisions ( only in one direction)
Use 1. Conservation of Momentum. 2. Newton's Law of Restitution. 3. Simultaneous Equations.
Solve: Oblique Collisions at impact the centres are aligned in the "i" direction.
Use the CM and NEL on the "i" components. The "j" components are unchanged.
Solve: Oblique Collision at impact the centres are at an awkward angle. Find the angle:
Draw a good diagram of the moment of impact. Form a right angled triangle between the centres. The Hypotenuse = 2r.
Have your diagram clearly. Physically rotate the page. Draw your new "i" and "j" components.
Solve: Oblique Collision at impact the centres are at an awkward angle. Rotate the coordinate system:
Solve: Oblique Collision: the angle through which the sphere is deflected:
Get the slopes of the initial and final vectors. ( Slope = "j comp" / "I comp"). Use the formula: Tan θ = ± (m₁ − m₂) ÷ (1+m₁ m₂).
Ep = mgh
Collisions with Strings (like Newtons Cradle)
Use Conservation of Energy: Lost Potential Energy = Gained Kinetic Energy to find the velocity at impact.
At least 10 feet skid apart caused by releasing break
1-3 foot gap cause by bouncing, pedestrian impact, or pot holes. Interrupted skid
Ghost like skid, caused by locking of breaks. Not quite leaving a skid.
Caused by road sloping, unequal breaks, unequal road surface. Measure full length of skid. Do not go in straight line
Skids that go from light to dark to light to dark. Continuously interrupted by breaking system.
Cause by all 4 or 2 tires on one side locking up. Measure entire length and subtract the wheel base.
Caused by vehicle spinning. Measure entire length as on surface.
Sudden change during skid because of impact. Noted as collision scrubs.
On map road component
1 tenth mile/ 500ft on straight level road.
Rarely requires quick decision making
Requires quick decision making. Actions taken by driver to avoid collision.
1.6 seconds. My be affected by age, strength, physical condition, habits, and perception delays.
Components of highway transportation system
4 kinds of info doc for each
People component 5 categories
Driver has control over
Driver has no control over
Impact in center mass. Little or no rotation
Impact not in center mass resulting in rotation after impact.
Major events of collision
Point of possible perception
Point of actual perception
Not present in all collisions
A situation in which two objects in close contact exchange energy and momentum
Sequence of events that usually produce unintended injury, death or property damage.
A force that "touches" or comes in contact with the system
(physics) the capacity of a physical system to do work
A force exerted on an object without touching it
(interactions between two objects)
a contact force; type of force between two touching surfaces
(physics) the force of attraction between all masses in the universe
transfer of energy due to a difference of temperature. The form of energy that is transferred between two substances because they have different temperatures.
The variable changed on purpose in an experiment; all others should be kept the same.
_______ is the property of an object that leads it to resist any change in motion
Acceleration depends on the
(physics) a rate of change of velocity
adj. in a state in which equal and opposite forces cancel each other out
(mass) x (g) x (height)
(physics) the rate of doing work
Changes in this variable need to be measured in an experiment; its value should change due to intentional changes in another variable.
Units: cm/s, m/s, mi/hr, km/s ...
lift, in the air (planes/birds)
Unequal forces acting on an object is a _______ force.
A change from one form of energy to another is called_______
A major blood vessel which carries blood away from the heart to the rest of the body.
Conservation of Energy
Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes
Describe the tension in a freely running massless rope
A major blood vessel which carries blood back to the heart from the lungs or from the body.
A force that comes from gravity pulling down on any object with mass
a force acting upon an object to cause a displacement. (key words: force, displacement, and cause)